/Engine/Source/Runtime/Engine/Classes/Kismet/KismetMathLibrary.h
Breaks apart a color into individual HSV components (as well as alpha) (Hue is [0..360) while Saturation and Value are 0..1)
static void RGBToHSV ( [FLinearColor](API\Runtime\Core\Math\FLinearColor) InColor, float & H, float & S, float & V, float & A )